High-tension bushing transformer



Jan. 1, 1929.

F. ANDORFF v HIGH TENSION BUSHING TRANSFORMER Filed Dec. 13, 1926 Patented Jan. 1, 1929.

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PATENT OFFICE.

GERMANYQIASSIGNOR T0 AKTIENGESELL SCH AIT BROFN, IBOVERI & CIR, OF BADEN, SWITZERLAND, A JOINT-STOG'K COMPANY.

HIGH-TENSIOK BUSHING TRANSFORMER.

Application filed December 13, 1926, Serial R0.

This invention relates to'lead bushings for high voltage apparatus, such as circuit breakers, or transformers; and it has particular relation to, instrument transformers, or similar devices associated with such bushings.

Diificulties are very often experienced in the construction of instrument transformers for high voltage apparatus, inasmuch as the low voltage windings must be maintained at a relatively low potential. so as to eliminate any danger to the metering and switching equipment and personnel which comes in contact therewith, and ithas, on the other hand, to be closely interlinked-with the high voltage parts of the circuit with which it is to co-operate in transformer relationship.

I The difliculties are less pronounced in cases Where single-turn current transformers ma be provided inasmuch as the straight throug conductors passing through the walls of the high voltage apparatus in the center of the lead bushings may be utilized astheprimary winding, and the. secondary winding may be arranged on an iron core disposed concentrically about the bushings. This simple construction becomes, however, inadequate where the current in the high voltage lead is low, such as is the case in all the high voltage transformer and circuit breaker stations wherein the problem of the provision of suitable instrument transformers is most acute, inasmuch as the current in the single-turn primary is not sufficient to produce the flux reformerof the foregoing character that will quired for satisfactory operation of trans formers. In such cases, the construction of the instrument transformers becomes very cumbersome and expensive, and renders the high voltage apparatus more complicated than is desirable from the standpoint of satisfactory operation.

The objects of my invention aim at the provision of an improved instrument transavoid the deficiencies of the prior-art constructions, and that will permit the construction of high voltage transformer windings of any desirable number of turns,'with bushings of the' ordinary type, such as have been used heretofore in instrument transformers operated with single-turn high voltage rimaries. According to my invention, the aminated and suitable barriers 154,445, and inGermany December 24, 1925.

suitable secondary winding .is arranged onthe core, preferably in the interior ofxthe bushing, to co-operate with the high voltage windlng, the bushingsebeing filled with oil,

sulate the high-voltage winding against the low-voltage winding-and the core.

My invention may be embodied in of constructions some of which by way of example, drawings wherein Fig. 1 is a vertical sectional view of a bushmg transformer and a portion of the high voltage apparatus made according to the invention;

Fig. 2 is a transverse sectional view through fie gliansformer of Fig. 1 along the line.-

Figs. 3 and 4 are views similar to Fig. 1 showing modifications of the invention;

Fig. 5 is a view similar to Fig. 2 through a variety in the accompanying thedtransformer of Fig. 4 along the line V- an Figs.- 6 and 7 are views similar to Fig. 1 of further modifications of my invention. I As pointed out above, the principal feature of the lnvention resides in the solution of the ,difliculties experienced in the provision of instrument transformers in con'unction with simple lead bushlngs. These ifliculties are solved by mounting the whole, or the main 3 and 4, having their inner ends 5 and 6 arranged to telescopically slide one within the other. The inner end 5 of the upper insulating member 3 is arranged to fit over the end are shown,

ing provided between the'wlndlngs and the cores so as to fully in 6 of the lower insulating member 4, so as to protect the interior chamber formed by the two insulating members from moisture, or.

rain, or other undesirable influences.

The two tubular insulating members are united into a single bushing by means of a pair of metallic flange members 7 and 8, which are suitably cemented to the upper and lower insulating members, respectively, the flanges 7 and 8' being tightly joined to each other to preventescape of insulating liquid,

' such as oil,,which fills-the hollow chamber 9 circular spaces between the central core 11' and the outer circular core portion 12. The

. stituting the high-Voltage coil of the trans of the bushing. The laterally projecting flanges 7 and 8 are suitably clamped to the 'wallsof the casing 1 ofthe high voltage apparatus.

As pointed out above, the essential feature of the invention'resides in the mounting of the principal elements of the instrument transformer within the interior of the bush ing so as to permit the utilization of multiturn primary windings, special complicated construction. In the exemplification of'the inventionshown in Fig.

1, this is'achieved by providing a suitable winding 13 having suitable leads which may I be connected to the metering and switching equipment in any approved manner, while the high volta e winding of the transformer is constituted ya number of turns 1-5 of the lead wire wound around the central core-and insulated from the core portions and from the low-voltage winding by means of insulating tubes 16', of porcelain for instance, the insu ating tubes extending through the semifree ends 21, 22 of the upper and lower tubular insulating members 3 and 4 are enclosed by suitable metallic closure members '23, 24, to which the ends of the lead wire 15, con-v former in the interior of the bushing are connected, so that the interior-closure member 24 may be used as a terminal connection to the high-voltage apparatus in theint-erior of the casing, while the outer-closure member 23 may be used as the exterior terminal of said apparatus.

A distinct feature of the invention resides in the simple arrangement for holding or supporting the transformer core. within the hollow chamber in the interior of the bushing, so as to prevent short circuits or other defects that may result from accidental diswithout recourse to pl a'cenierit of the parts within the interior of the bushing. Thls improved mounting also permits ready dismantling of the bushing and the removal of the transformer'from within the interior of the bushing for overhauling or repair, without necessitating the removal of the entire bushing from the easmg. 1

To this end the transformer is so arranged as to be directly or indirectlyheld in place by intermediate conducting flange members 1 7 and 8 which join the upper porcelaintube 3 to the lower porcelain tube 4 of the bushing.

In the exemplification of the invention shown in Fig. 1, the circular core 12 is clam I ed be-' tween the inwardly projecting shou der or ledge 26 of the upper insulator, and the upper edge of the tubular end portion6 of the lower insulator 4, which projectsinto the interior of the upper insulator. The pressure required tohold the annular magnetic core 12 7 between the two porcelain members is supplied by the means which serve to clamp the flanges 7 and 8 to each other, the metallic clamping members thus serving indirectly to hold the transformer in'place. In order to disassemble the bushing for inspection or repair of the transformer, it is sufficient to release the bolts .or other means with which the upper flange 7 is held to the lower flange 8.

The upper bushing member 3 may then be re-' moved and the transformer core 11' 12 with the associated windings readily dismantled.

The bushings that are ordinarily-used on high voltage have a filling of oil or other insulating liquid in order to effectively insulate the high-voltage lead wires 15. The present improved mounting of the instrument transformer within the bushing represents very marked advantages in cases where air or gaseous msulation within the bushing is 'sufficient.

In Fig. 3 is shown a form of the invention. 'in which the lower half of the bushing insulatoris omitted, the casing 1 of the highvoltageapparatus being entirelyfilled with oil, whlch also extends towards the top of the bushing. The bushing comprises. a tubular insulator 31 having a flange member 32 cemented to the lower open end thereof, forjoining the bushing to the walls of the apparatus casing 1/ A current transformer of similar construction as that shown in Figs. 1

and 2, has the magnetic core 12 held in place by clamping the same between the inner edge of the casing 1 and the upper flange end '33.

The top of the tubular insulating bushing 31- has a constricted end portion which is sealed by a glass cap 34 for determining the level'of the oil in the bushing, enough oil always being maintained in the bushing and the casing so that the upper level thereof is visible in the glass cap 34.

The bushing shown in two similar shell halves 41, 42, which are Fig. 4 comprises joined to each other by means of flanges 43, 44. he iron core 12 of the current transformer is held between the flanges by means of aring 45 which extends from the core int'o the space between'the opposing surfaces of the flanges. z

'lhe bushing shown in Fig. 4 is also distinguished by a modified construction of the tubular porcelain insulator for insulating the high-voltage turns of the lead-in wires from the low-voltage winding and the core of the instrument transformer. 7

As shown in Fig. 5, the insulating tubes have the form of semi-circular cylinder sections, 46 similar in shape to the spaces between the central core member and the outer circular-core member-of the instrument transformer. The two tubular insulator members 46 are joined by cross members 47 to form a single piece and are held in placebetween suitableprojecting shoulders 48 of the upper and lowerhalv'es of the bushing. In View,

however, of the integral construction of the -1 two insulated tubes 46, the transformer core cannot be constructed from single-piece'laminations.

In the arrangement shown in Figs. 4 and 5 the middle leg 48 of the transformer is made distinct from the circular coreportion, the circular core portion havinginwardly. extending chamfered projections 49 against which abut similarly shaped end surfaces of the middle core leg. This construction insures a satisfactory magnetic joint between the core members, the joint being still further improved t-hrough the magnetic attraction of the. core portions.

In the modification of the invention shown in Fig. 6 the upper and lower bushing halves 51, 52, are joined by means of flanges, 53, 54, having cylindrical extension members 55, 56, that are cemented to the interior wall surfaces of the bushing members, the magnetic core 12 of'the transformer being secured to the inner portions of the flanges within the bushing.

In the modification of the invent-ion shown in Fig. 7, the bushing is formed of an upper tubular insulating member 61 and a lower insulating member 62 which are mounted coaxially with each other by means of an intermediate tubular member 63 of iron or similar conducting material, the intermediate memher being cemented to the adjacent ends of the upper and lower insulating members 61 and 62. The bushing is mounted on the casing of the hi h-voltage apparatus by means of a flange 6 laterally extending from the intermediate metallic portion of the bushing. The instrument transformer in the interior of the bushing is-held in place by clam .ing the transformer core 12 to a shelf member 66 extending fromthe walls of the intermediate metallic tiibe 63 towards the center of the bushing. The upper insulator is not structions described before,

core member being held in constricted at its top end as in the other conbut is sufficiently wide topermit the removal of the instrument transformer with lead-inwires 15 from the interior of the bushing, after the cap 67, which is clamped to the top of the bushing, has been removed.

I claim as my invention: I I

' 1. A lead-in bushing for high-Voltage apparatus comprising a tubular insulating mem-' her, said insulating member bein closed at its ends to constitute a closed cham r, a leadin'conductor extending-through said tubular member between the ends thereof, a magnetic core member disposed in the interior of said chamber, said lead-in conductor being wound around said core member to constitute a transformer winding, an additional winding wound around said core member to operate in transformer relationship with the said first-mentioned winding,- and insulating means disposed between the portions of the cad-in conductor adjacent to said core member within the interior of said bushing.

2. A lead-in bushing comprising a pair of coaxial insulating tubes, means for joining said tubes to each other, the free ends of said tubes being sealed, a lead-in conductor extending through said bushing between such endsthereof, a magnetic core member disposed in the interior of said bushing, said lead-in conductor constitutin a transformer winding wound around sai core member,

and another winding wound around said core member to operate in transformer relationship with said first-mentioned winding, said place by said means for joining said tubes.

3. A lead-in bushing-for high-voltage apparatus comprising a pair of coaxial tubular insulators, an annular'metal'lic member uniting said tubular insulators-said tubular insulators being closed at their ends to constitute in conjunction with said metallic memher a closed chamber, a lead-in wire extending through said chamber between the ends of said tubular insulators, a transformer core disposed in said chamber and held in place by said metallic member, said lead-in conductor constituting a transformer winding wound around said core, and an additional posed in the interior of said chamber and 5. A combination as defined by claim 4 held in place by said conducting member, said characterized by a fillingof insulating liquid lead-in conductor constituting a primary in said bushing chamber. 10 Winding Wound around said core, and an ad- In testimony whereof I have hereunto sub- 5 ditional Winding wound around said core in scribed my name at Mannheim, November 23,

transformer relationship with said first-men- A. D. 1926. tioned winding. FRITZ ANDORFE 

